Date: Thu, 9 Apr 1998 22:49:14 -0600 (MDT) From: "Justin T. Gibbs" <gibbs@narnia.plutotech.com> To: FreeBSD current users <FreeBSD-current@FreeBSD.ORG> Cc: FreeBSD-scsi@FreeBSD.ORG Subject: Re: compression on Exabyte 8700LT? Message-ID: <199804100449.WAA16931@narnia.plutotech.com> In-Reply-To: <199804091527.QAA09483@albatross.mcc.ac.uk> <19980410112408.01873@freebie.lemis.com>
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I don't know why this was sent to questions. It was started on SCSI
which seems to be where it belongs...
> -CURRENT people: I'm using the old SCSI driver. The tape is set to
> start up in compressed mode, and the DC LED is illuminated all the
> time. This looks to me as if something in the driver is explicitly
> disabling compression, or just possibly that the driver is guessing
> the size of the tape and stopping (with EIO) when it reaches this
> point.
Neither the old driver, nor the CAM driver performs any type of guessing
about the size of the tape.
> The other point is that it's still returning EIO. I know there's been
> some discussion about this before, and ISTR that it was inconclusive
> ("that's the way our grandfathers did it"). While looking at the
> problem, I came across a program I wrote in my BSD/OS days back in
> 1992, and I note that even then BSD/OS returned ENOSPC when it got to
> the end of the tape. This makes a whole lot more sense, and it
> obviously seems to have withstood the test of time. How about it?
The decision was that it should return ENOSPC. The CAM driver does
return ENOSPC. I have patches, in my CAM tree, to ensure that dump
and restore correctly deal with ENOSPC as an EOT condition. Someone
should probably check pax, cpio, and tar.
> Would I get an improvement on either of these points if I installed
> CAM?
Probably. You may want to wait for the weekend though. I'm "this close"
to finishing the BusLogic driver, and I intend to release a new snapshot
at that time. This will also include some improvements to the tape driver.
> I know that CAM can't handle compression switching yet, but can
> it do compression if it's enabled on the drive?
The next snapshot will have compression and density control support.
Ken's already implemented, and tested it.
> Greg
--
Justin
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